<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    while(true){
      let username=prompt('输入用户名')
      let password=prompt('输入密码')
      if(username==='admin'&&password==='123456'){       
        break
      }
    }
    alert('登录成功')
  </script>
</body>
</html>